The present invention relates to a CVD film forming method and apparatus for forming a film or layer by CVD on an object to be processed, such as a semiconductor wafer.
In the process of manufacturing a semiconductor device, a metal or metallic compound film is formed on a semiconductor wafer made of, for example, silicon, by CVD (Chemical Vapor Deposition), so that an integrated circuits can be formed on the wafer. For example, an Al film is formed on the main surface of the semiconductor wafer as follows. First, the semiconductor wafer is placed on a susceptor with an electrostatic chuck in a process chamber. The susceptor has a ceramic base member in which a heating member is embedded. While the semiconductor wafer is being heated by electricity supplied to the heating member, a process gas, e.g., dimethylaluminumhydride (DMAH) is introduced at a predetermined flow rate into the process chamber through a shower head provided above the susceptor. As a result, an Al film is formed on the surface of the semiconductor wafer.
To form an Al film, an electrostatic chuck having a diameter slightly smaller than that of the semiconductor wafer is used. The semiconductor wafer is held on the susceptor such that the circumferential edge of the semiconductor wafer is slightly projected from the electrostatic chuck, thereby preventing film formation on the electrostatic chuck.
However, in this case, the process gas flows to the rear surface of the projected portion of the semiconductor wafer and a film is formed thereon. If a film is formed on the rear surface of the semiconductor wafer, the film may be removed during a transfer or other processes, resulting in particles.